Ink jet printing is a well-known technique by which printing is accomplished without contact between the printing device and the substrate on which the printed characters are deposited. Briefly described, ink jet printing involves the technique of projecting a stream of ink droplets to a surface and controlling the direction of the stream, e.g., electronically, so that the droplets are caused to form the desired printed message on that surface.
The technique of ink jet printing or non-contact printing is particularly well suited for application of characters onto irregularly shaped surfaces, including, for example, glass, metal, or plastic containers, generally used for holding beverage, cosmetic, pharmaceutical, liquor, and health care products.
Reviews of various aspects of ink jet printing can be found in the following publications: Kuhn et al., Scientific American, April, 1979, 162-178; and Keeling, Phys. Technol., 12(5), 196-303 (1981). Various ink jet apparatuses are described in the following U.S. Pat. Nos. 3,060,429, 3,298,030, 3,373,437, 3,416,153, and 3,673,601.
In general, an ink jet ink composition must meet certain rigid requirements to be useful in ink jet printing operations. These relate to viscosity, resistivity, solubility, compatibility of components, and wettability of the substrate. Further, the ink jet ink composition must be quick-drying and smear resistant, resist rubbing, and be capable of passing through the ink jet nozzle without clogging, and permit rapid cleanup of the machine components with minimum effort.
In addition, the ink jet ink composition must meet certain other requirements. Many beverage manufacturers fill the containers with chilled beverages, frequently under humid conditions that promote condensation of moisture on the containers. The moisture that condenses on the container surfaces poses a severe problem in obtaining ink penetration, good adhesion, and abrasion resistance of the printed messages. Thus, the ink jet ink composition should allow printing on these containers in the presence of a certain level of condensation, and the printed messages should not be damaged by the condensation. Further, when the containers are immersed in ice water for chilling or exposed to hot water during pasteurization, the printed messages should not disintegrate or be damaged by such treatments. Moreover, the bottles may be exposed to warm and humid conditions, e.g., during warehousing and shipping to different parts of the world and in different seasons. The messages should not be damaged by the hot and cold humid conditions.
A few ink jet ink compositions are reported to be suitable for printing on glass surfaces. For example, U.S. Pat. No. 5,596,027 discloses in an embodiment, a water-based jet ink composition comprising a colorant, a polyamine, and an acidic resin. It is known that water-based inks take a relatively long time to dry on glass substrates. Drying times greater than 10 seconds may be necessary with water-based inks. U.S. Pat. No. 6,221,933 discloses an ink jet ink composition comprising an ink carrier, a colorant, a polyamine, and an acidic resin. This ink composition is capable of producing condensation and moisture resistant images on clear or lightly colored glass surfaces. U.S. Pat. No. 5,652,286 discloses a jet ink composition comprising an organic solvent, a flexible thermoplastic urethane resin, a silicone resin, and a colorant.
Many of the known ink jet ink compositions are not suitable for printing on glass under humid conditions, or do not provide water resistant printed messages on glass surfaces. U.S. Pat. No. 5,693,127 discloses a jet ink comprising a binder, a colorant, a liquid vehicle and an adhesion promoter which is an alkoxysilyl polyalkylene-imine. Although the patent states that the ink is suitable for printing on glass bottles having condensation thereon, certain difficulties are encountered in following its teachings. For example, the alkoxysilyl polyalkylene-imine adhesion promoter does not appear to be commercially available, and the patent does not teach those of ordinary skill in the art how to make this adhesion promoter. Further, the stability of the ink composition containing alkoxysilyl polyalkylene-imines remains uncertain. Additionally, the composition, while suitable for printing on clear or light glass surfaces, does not provide an opaque ink suitable for printing on dark glass surfaces.
U.S. Pat. No. 5,744,519 discloses an ink composition comprising at least one dye, an organic solvent and a binder incorporating the combination of at least one polymeric resin having hydroxyl or carboxyl functions and a hydrophobic polymeric resin of the epoxy type. However, the patent does not suggest ways of producing opaque ink compositions providing good adhesion, good condensation and water resistance and good contrast on dark glass containers.
Thus, there exists a need for an opaque ink jet ink composition meeting one or more of certain critical performance requirements. There exists a need for a fast drying opaque ink jet ink composition that provides high quality messages on various surfaces, particularly darkly colored glass surfaces which may have a condensation of moisture on them. There also exists a need for an opaque ink jet ink composition whose printed messages do not smear, rub off, or otherwise degrade when exposed to moisture, such as ice water immersion, hot water immersion, and/or hot and cold humid conditions.
The advantages of the present invention as well as additional inventive features, will be apparent from the description of the invention provided herein.